Electronic endoscope selector

ABSTRACT

An electronic endoscope selector that is used in an electronic endoscope system which shares peripheral devices, such as a TV monitor, VCR etc., among a plurality of electronic endoscopes. The electronic endoscope selector comprises switching circuits for switching and selecting video signals and synchronizing signals fed from one of the plurality of electronic endoscopes in the system. The selector also comprises ON/OFF switches and a timer. The ON/OFF switch controls output of the selected video signals. When the switching circuits switch between the plurality of electronic endoscope and switch video signals and synchronizing signals to that of a newly selected electronic endoscope, the output of video signals are suspended during a predetermined period, by the timer. On the other hand, the synchronizing signals are output simultaneously with the above switching.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic endoscope system, whichcomprises a plurality of electronic endoscopes and peripheral devices,such as TV monitors or VCR's (video cassette recorder).

2. Description of the Related Art

In recent medical practice, various types of electronic endoscopesystems, such as the RGB sequential or color chip systems, an ultrasonicsystems, a system that captures a fluorescent image of exited cells inthe interior of a hollow organ and so on, are used. Each electronicendoscope system is selectively utilized as the occasion may require. Inelectronic endoscopy, dissimilar to optical endoscopy that observes anoptical image at the distal end of a fiber-optic bundle, an imagingdevice, such as a TV monitor, is required to observe the image capturedby the above electronic endoscope.

In a large number of medical facilities, several types of electronicendoscope systems are utilized during a single checkup or medicalexamination since each type of electronic endoscope system has anexclusive purpose. In these facilities, it is the dissipation of spaceand cost of peripheral devices, such as TV monitors, video cassetterecorders and so on, provided for each electronic endoscope system. Itis also cumbersome and time consuming to operate the peripheral devicesindividually prepared for each system.

SUMMARY OF THE INVENTION

Therefore, it is preferable to share devices that have a common functionamong the electronic endoscope systems, such as a TV monitor, videocassette recorder (VCR), etc., and build a single organized electronicendoscope system. In order to share the peripheral devices among theplurality of electronic endoscope systems and build an organizedelectronic endoscope system, an electronic endoscope selector thatmediates between each of the electronic endoscopes and the- peripheraldevices is required.

The above organized electronic endoscope system comprises a plurality ofelectronic endoscope units, each of which comprises an endoscope with anelongated part for insertion into a body cavity or hollow organ, and animage-signal processing unit that processes image signals fed from animaging device mounted on the distal end of the elongated part of theendoscope. Images captured by the imaging device are output from theimage-signal processing unit to the electronic endoscope selector asvideo signals with a synchronizing signal. It takes time for the TVmonitor to synchronize with the synchronizing signal fed from the newlyselected electronic endoscope and if the electronic endoscope selectorsimultaneously switches both video signals and synchronizing signal fromone electronic endoscope unit to another, unsynchronized video will bedisplayed on the TV monitor while the TV monitor is synchronizing withthe synchronizing signal. Therefore, the electronic endoscope operatorinevitably observes unsynchronized image on the TV monitor while the TVmonitor is engaged in the synchronizing operation. This causes eyestrainto the operator, especially when the TV monitor is used in a darkenedroom to improve the observation of the image.

Therefore, an object of the present invention is to provide anelectronic endoscope selector that enables a plurality of electronicendoscopes to share a peripheral device and integrate a plurality ofelectronic endoscope systems into a single organized electronicendoscope system. Further, the object of the present invention is toprovide the electronic endoscope selector, which sends video of aselected electronic endoscope to a peripheral device withoutunsynchronized video when the electronic endoscope is switched toanother electronic endoscope.

According to the present invention, there is provided an electronicendoscope selector comprising a video signal switching processor, asynchronizing signal switching processor and a switching controlprocessor.

The video signal switching processor switches video signals, output toat least one peripheral device, between first video signals fed from afirst electronic endoscope to second video signals fed from a secondelectronic endoscope. The synchronizing signal switching processorswitches synchronizing signals, output to the peripheral device, betweensynchronizing signals fed from the first electronic endoscope tosynchronizing signals fed from the second electronic endoscope. Theswitching control processor drives the video signal switching processorand synchronizing signal switching processor and suspends output of thevideo signal for a predetermined period after driving the synchronizingsignal switching processor.

Preferably, the electronic endoscope selector comprises an operatingprocessor for driving the switching control processor.

The switching control processor may drive the video signal switchingprocessor and the synchronizing signal switching processorsimultaneously. In this case, preferably, the switching controlprocessor comprises an output switching processor and a timer. Theoutput switching processor switches the video signals between the ‘ON’and ‘OFF’ states. The ON state permits and the OFF state forbids outputof the video signals. The timer is used for timing the predeterminedperiod. Further, the output switching processor is set to ‘OFF’ and thetimer is started when the synchronizing signal switching processor isdriven. Furthermore, the output switching processor is switched to ‘ON’after the predetermined period. The ‘ON’ and ‘OFF’ states for outputcontrol of the video signals from the video signal switching processorare switched by the output switching processor.

In another preferable example, the switching control processor drivesthe video signal switching processor for a predetermined period afterdriving the synchronizing signal switching processor, and suspendsoutput of the video signals for a predetermined period.

Further, preferably, the signal switching processor comprises a firstand second buffer circuit and the switching control processor comprisesa first and second timer.

The first buffer circuit, to which input the first video signals are fedfrom the first electronic endoscope, controls the ON and OFF states ofvideo signal output. The ON state permits video signal output, and theOFF state forbids video signal output. The second buffer circuit, towhich input the second video signals are fed from the second electronicendoscope, controls the ON and OFF state of the video signal output. Thefirst timer sets the first buffer circuit to the OFF state, whichforbids output of the video signals, immediately after receipt of acontrol signal. The second timer sets the second buffer circuit to ‘OFF’state immediately after input of a control signal. It also sets thesecond buffer circuit to ‘ON’ after a predetermined period from controlsignal input completion. Therefore, switching of the first and secondvideo signals is controlled by the control signal, which is inputalternately to the first and second timer.

Furthermore, the synchronizing signal switching processor comprises athird and fourth buffer circuit. The third buffer circuit receivessynchronizing signals from the first electronic endoscope and controlsthe ON and OFF states of synchronizing signal output. The ON statepermits output of the synchronizing signals and the OFF state forbidsoutput. The fourth buffer circuit receives synchronizing signals fromthe second electronic endoscope and controls the ON and OFF states ofsynchronizing signal output. Switching the synchronizing signals iscontrolled by alternating the ON and OFF states of the third and fourthbuffer circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will be betterunderstood from the following description, with reference to theaccompanying drawings in which:

FIG. 1 is a schematic showing an electrical construction of anelectronic endoscope system that is integrated with an electronicendoscope selector of the first embodiment of the present invention;

FIG. 2 is a schematic showing an electrical construction of anelectronic endoscope selector of the second embodiment; and

FIG. 3 is a circuit diagram of the timers shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below with reference to theembodiments shown in the drawings.

FIG. 1 is a schematic showing an electrical construction of anelectronic endoscope selector of the first embodiment of the presentinvention. In the figure, two types of conventional electronicendoscopes are connected to the electronic endoscope selector. Note thatthe optical components for illumination in the electronic endoscopeunits are omitted.

The TV monitor 20, the VCR 21 and the image-signal processing units 42,64 are connected to the electronic endoscope selector 10. Theimage-signal processing unit 42 is for processing image signals capturedby the conventional RGB sequential method. The image-signal processingunit 64 is for processing the image signals captured by a conventionalcolor chip method. Namely, an endoscope 30 that captures images in theRGB sequential method is detachably attached to the image-signalprocessing unit 42 and an endoscope 50 that captures images in the colorchip method is detachably attached to the image-signal processing unit64. Images captured by the endoscope 30 or 50 are alternativelydisplayed on the TV monitor 20. This alternative selection of the imagesdisplayed on the TV monitor 20 is switched by operating the electronicendoscope selector 10. The images displayed on the TV monitor 20 may besimultaneously recorded on a videocassette tape by the VCR 21.

Firstly, the flow of image and video signals in the first electronicendoscope unit, which comprises the endoscope 30 and the image-signalprocessing unit 42, is described.

The imaging device 31 is provided at the distal end of the elongatedpart of the endoscope 30. Images from within body cavities or holloworgans are captured by the imaging device 31 as image signals and outputvia cables inside the endoscope 30, to the image-signal processing unit42. The image signals, input to the image-signal processing unit 42, areamplified by a preamplifier (not shown), and then input to theprepositional processing circuit 32. In the prepositional processingcircuit 32, filtering of video bandwidth, S/H (sample hold), amplifying,clamping, clipping and gamma correction processes, etc., are executed tothe image signals. The signals are then converted to digital imagesignals and output from the prepositional processing circuit 32.

In the RGB sequential method, the images are sequentially captured inunits of R (red), G (green) and B (blue) color images, thus the digitalimage signals output from the prepositional processing circuit 32 arealso sequential signals of the R, G and B images. Each of the R, G and Bimage signals is transferred to, and temporary stored in, a respectiveimage memory 33, 34 and 35 in accordance with the timing of the imagesignals. Namely, image data of the respective R, G, B images areseparately stored in the corresponding image memory 33, 34 and 35.Timing for outputting and storing the RGB image signals at theprepositional processing circuit 32 and the image memory 33, 34 and 35is controlled by the timing controller 36.

When one set of image data comprising R, G and B images are prepared inthe image memory 33, 34 and 35, the individual R, G, B image data isconverted to analog signals and output to the respective postpositionalprocessing circuit 39, 40 and 41. In each of the postpositionalprocessing circuits 39, 40 and 41, a filtering, amplifying, gammacorrection, clamping, clipping, enhancing, signal level adjustmentprocess and so on, are executed to each of the R, G, B image signals andtransformed to the conventional standardized RGB component format, inother words RGB component video signals. Timing the output of the R, G,B image signals from the image memory 33, 34, 35 and driving thepostpositional processing circuits 39, 40 and 41 is controlled by thetiming controller 36.

The prepositional processing circuit 32, the timing controller 36 andthe postpositional processing circuit 39, 40 and 41 are controlled bythe system control circuit 37. The system control circuit 37 is alsoconnected to the control panel 38, which is arranged with operatingswitches (not shown), and controlled by instruction signals generated inthe control panel 38 when the switches on the panel are operated.

The RGB component video signals R1, G1 and B1, output from therespective postpositional processing circuits 39, 40 and 41, are fed tothe switching circuits 11, 12 and 13 of the electronic endoscopeselector 10 respectively, via the cables. At the same time, thesynchronizing signal T1 is output from the timing controller 36 to theswitching circuit 14 of the electronic endoscope selector 10.

The flow of image and video signals in the second electronic endoscopeunit, which comprises the endoscope 50 and the image-signal processingunit 64 is described as follows:

The imaging device 51 is provided at the distal end of the elongatedpart of the endoscope 50. At the imaging device 51, which is adapted forthe color chip method, the R, G and B image signals for any one fieldare individually and simultaneously obtained. Images of a body cavity orinterior of a hollow organ, captured by the imaging device 51, areoutput as image signals via the cables inside the endoscope 50, to theimage-signal processing unit 54. The image signals, input to theimage-signal processing unit 64, are appropriately amplified by apreamplifier (not shown), then input to the prepositional processingcircuits 52, 53 and 54. In the prepositional processing circuits 52, 53and 54 a filtering of video bandwidth, S/H (sample hold), amplifying,clamping, clipping and gamma correction processes, etc., are executed tothe image signals. The signals are then converted to digital imagesignals and output from the prepositional processing circuits 52, 53 and54.

Each of the digital RGB image signals output from the respectiveprepositional processing circuits 52, 53 and 54 are temporally stored inthe respective image memory 55, 56 and 57. Namely, image datacorresponding to each of the R, G, B images are individually stored ineach of the image memory 55, 56 and 57, respectively. The R, G, B imagedata stored in the image memory 55, 56, 57 is converted to analogsignals and fed to each of the postpositional processing circuits 61, 62and 63. In each of the postpositional processing circuits 61, 62 and 63,a filtering, amplifying, gamma correction, clamping, clipping, enhancingand signal level adjustment processes, etc., are executed to each of theR, G, B image signals and transformed in to conventional standardizedRGB component video signals.

Timing for the prepositional processing circuits 52, 53, 54, the imagememories 55, 56, 57 and postpositional processing circuits 61, 62, 63 iscontrolled by the timing controller 58. The prepositional processingcircuits 52, 53, 54, the timing controller 58 and the postpositionalprocessing circuits 61, 62 and 63 are controlled by the system controlcircuit 59. The system control circuit 59 is connected to the controlpanel 60, which is arranged with operating switches (not shown), and itis controlled by instruction signals generated by the control panel 60when the switches on the panel are operated.

The RGB component video signals R2, G2 and B2, output from therespective postpositional processing circuits 61, 62 and 63, are fed viathe respective cables to the switching circuits 11, 12 and 13 of theelectronic endoscope selector 10. At the same time, the synchronizingsignal T2 is output from the timing controller 58 to the switchingcircuit 14 of the electronic endoscope selector 10.

Switching operations among the RGB component video signals and thesynchronizing signals, which are executed in the electronic endoscopeselector 10, are explained as follows:

Each of the switching circuits 11, 12, 13 and 14 has a plurality ofinput channels and a single output channel. The switching circuitswitches the selection among the input channels so that only signalsfrom a single selected input channel may be output from the outputchannel. In this embodiment, there are two input channels in eachswitching circuit. Examples of the switching circuit are a conventionalanalog switch, a relay and so on. The RGB component video signals, whichare output from the switching circuits 11, 12 and 13, are fed to theON/OFF switches 15, 16 and 17, then transported to the TV monitor 20 andVCR 21 via the cables. On the other hand, the synchronizing signalsoutput from the switching circuit 14 are directly fed to the TV monitor20 and VCR 21 via the cables, and there is no ON/OFF switch providedbetween the switching circuit 14 and the peripheral devices. Note that,examples of the ON/OFF switches 15, 16, 17 are also a conventionalanalog switch, relay and so on.

The switching operations at the switching circuits 11 through 14 arecontrolled by instruction signals from the control panel 19. Further,these switching operations in the switching circuits 11 through 14 areexecuted simultaneously. Namely, when an operator operates a switch onthe control panel 19 to switch the selected electronic endoscope, theoutput signals from each of the switching circuits 11-14 are switched tothe alternative signals concurrently. Since output signals from theswitching circuit 14 are directly fed to the TV monitor 20 and the VCR21, the newly selected synchronizing signals are transferred to the TVmonitor 20 and VCR 21 immediately the switching operation is executed.

On the other hand, ON/OFF switches 15, 16 ,17 are switched to the OFFstate when the switching operation is executed, and at a predeterminedtime after the switching operation, they are switched to the ON state.Namely, the RGB component video signals, which are fed from theswitching circuits 11, 12, 13 to the TV monitor 20 or VCR 21 via ON/OFFswitches 15, 16, 17, are output to the TV monitor 20 and VCR 21 onlyafter a predetermined time has passed after the switching operation onthe control panel 19. During this period, no image is displayed on theTV monitor 20 and the screen of the TV monitor 20 is blank.

Switching operations at the ON/OFF switches 15, 16, 17 are controlled bya signal from the timer 18. The above predetermined time, the timebetween the beginning of the OFF state and the beginning of the ON statein the ON/OFF switches 15, 16, 17, is sufficient, several minutes forexample, for the peripheral device, the TV monitor 20, VCR 21 and etc.,to synchronize with the synchronizing signals fed from a newly selectedelectronic endoscope unit. Note that, the timer 18 is a conventionaltimer, for example, a timer that counts the number of clock pulses froma clock pulse generator, a timer that utilizes the time constant of aR-C circuit, and so on.

As discussed above, according to the first embodiment, an electronicendoscope selector that is able to switch pictures on a display devicesuch as TV monitor, without displaying unsynchronized video on thedevice, is obtained.

With reference to FIG. 2 and FIG. 3, an electronic endoscope selector ofa second embodiment of the present invention is described.

FIG. 2 is a schematic showing the electrical construction of anelectronic endoscope selector of the second embodiment. The electronicendoscope selector 70 is comprised of eight buffer circuits 71 a, 71 bthrough 74 a, 74 b, two timers 75, 76 and a control panel 78.

The component video signals R1 output from the first electronicendoscope unit and the component video signals R2 output from the secondelectronic endoscope unit, as shown in FIG. 1, are input to the buffercircuits 71 a and 71 b respectively. Similarly, the component videosignals G1, G2 are input to the buffer circuits 72 a, 72 b, and thecomponent video signals B1, B2 are input to the buffer circuits 73 a, 73b. Note that, each of the input signals G1, G2, B1 and B2 is identicalwith the component video signals shown in FIG. 1. Further, thesynchronizing signals T1 and T2, which are shown in FIG. 1, are input tothe buffer circuits 74 a and 74 b, respectively.

An example of the buffer circuits is a cable driver of which output iscontrolled by signals applied to its control terminal. The controlsignals applied to the control terminal of the buffer circuit 71 a-74 a,71 b-74 b comprise of two states, such as a high level ‘H’ and a lowlevel ‘L’. When the control signals of the buffer circuits 71 a-74 a, 71b-74 b are ‘H’, the impedance of the output terminals of the buffercircuits 71 a-74 a, 71 b-74 b is high. Contrary, when the controlsignals of the buffer circuits 71 a-74 a, 71 b-74 b are ‘L’, the RGBcomponent video signals and the synchronizing signals are output fromthe output terminal of the buffer circuits 71 a-74 a, 71 b-74 b. Namely,the buffer circuits 71 a-74 a, 71 b-74 b are a device, which is able tooutput the signals when the control signals applied to the controlterminals are a low level ‘L’ and unable when the control signals are ahigh level ‘H’. Also, each pair of output terminals of the buffercircuits are directly interconnected i.e. 71 a with 71 b, 72 a with 72b, 73 a with 73 b, 74 a with 74 b.

The buffer circuits 71 a-74 a, 71 b-74 b output a set of RGB componentvideo and synchronizing signals, which are alternative sets of R1, G1,B1, T1 signals and R2, G2, B2, T2 signals, from the alternative firstand second electronic endoscope units. Either set of above signals isfed to the TV monitor 20 and VCR 21 in accordance with control signalsfrom the control panel 78.

The leads S1, from the control panel 78, are connected to the controlterminal of the buffer circuit 74 b and an input terminal of the timer75. On the other hand, the leads S2 from the control panel 78 areconnected to the control terminal of the buffer circuit 74 a and aninput terminal of the timer 76. An output terminal of the timer 75 isconnected to control terminals of the buffer circuits 71 b, 72 b and 73b via the leads S1′, and an output terminal of the timer 76 is connectedto the control terminals of the buffer circuits 71 a, 72 a and 73 a viathe leads S2′.

Therefore, while the component video signals from the first electronicendoscope unit is selected in the electronic endoscope selector 70,signals applied to the leads S2 and S2′ are kept in the low level L,thus the output terminals of the buffer circuits 71 a, 72 a, 73 a and 74a are ready to output the input signals. Contrarily, the leads S1 andS1′ are kept in the high level H, and the impedance of the outputterminal of the buffer circuits 71 b, 72 b, 73 b and 74 b is high. Thus,at this time, signals output from the electronic endoscope selector 10are signals from the buffer circuits 71 a, 72 a, 73 a and 74 a only.Namely, the set of R1, G1, B1 and T1 signals only are output to the TVmonitor 20 and VCR 21.

When an operator selects a switch on the control panel 78 to switch thevideo output fed from the first electronic endoscope unit to the secondelectronic endoscope unit, the status of leads S2 and S2′ immediatelychanges from the low to the high level. Namely, the impedance of theoutput terminals of the buffer circuit 71 a, 72 a, 73 a and 74 a becomeshigh, and as a consequence, output from the buffer circuits 71 a, 72 a,73 a is 74 a are forbidden.

The control signals in the leads S1 are also changed from the high tothe low level, simultaneous with the operators selection with the switchon the control panel 78, and the output terminal of the buffer circuit74 b is switched to allow output. Namely, the synchronizing signal T2 isoutput to the TV monitor 20 and VCR 21 simultaneously with the aboveswitching operation. On the other hand, the status of the leads S1′ ischanged from the high to the low level only after a predetermined timehas passed. Namely, the timer 75 and the timer 76 immediately switch theoutput signals to the high level when the input signals are switchedfrom ‘low’ to ‘high’ to stop video signal output, however, when theinput signals are switched from ‘high’ to ‘low’, they switch the outputsignals from ‘high’ to ‘low’, to allow video signal output only after apredetermined time. Therefore, the output terminals of the buffercircuits 71 b, 72 b and 73 b are able to allow output of the RGBcomponent video signals of the second electronic endoscope unit, thevideo signals R2, G2 and B2, to the TV monitor 20 and VCR 21 only aftera predetermined time has elapsed from the switching operation by theoperator. Note that, as in the first embodiment, the above predeterminedtime is a time necessary and sufficient for peripheral devices like theTV monitor 20 and VCR 21 to synchronize with the synchronizing signalsfrom an electronic endoscope unit. In other words, only video that issynchronized with the synchronizing signals of an electronic endoscopeunit is displayed on the TV monitor 20 and unsynchronized video is neverdisplayed on the monitor.

However, although the above description represents the case where videooutput is switched from the first electronic endoscope unit to thesecond electronic endoscope unit, the operation is the same when videooutput is switched from the second electronic endoscope unit to thefirst electronic endoscope unit.

Next, behavior of the timer 75 and timer 76 are explained with referenceto FIG. 3. FIG. 3 is a circuit diagram of the timers 75 and 76.

Firstly, action of the timers 75, 76, when the control signal or theinput signal V_(in) switches from the low to the high level, isexplained. The diode D is forward biased when the high level signal isapplied to the input terminal, so that current flows through the buffer80, the diode D, resistor R and charges the capacitor C. The currentflow causes a difference of electric potential between the two terminalsof the resistor R, and electric charge is accumulated in the capacitorC. The electric potential difference is compared with the electricpotential V_(ref) at the comparator 81. The potential V_(ref), forexample, is may be set to half the high level signal H, (H/2). When thepotential difference across the terminals of resistor R is greater thanthe reference potential V_(ref), the comparator 81 outputs a signalV_(out) as the high level signal H. Note that, when the potentialV_(ref) is set to the level H/2, the resistance of the resistor R ischosen so that the potential difference between the terminals of theresistor R is greater than level H/2 when the input signal V_(in) is thehigh level H. Namely, when the control signals output to the leads S1and S2 switch from the low level L to the high level H, and the inputsignals of the timers 75, 76 switch from L to H, the output signals fromthe timers 75, 76 are immediately switched to the high level H from thelow level L. Thus, the control signals output to the leads S1′ and S2′,connected to the respective output terminals of the timer 75 and timer76, immediately switch to the high level H from the low level L.

Contrarily, when the control signal, or input signal V_(in), switches tothe low level ‘L’ from the high level ‘H’, a reverse bias is applied tothe diode D. In this case, since electric charge has been accumulated inthe capacitor C, electric potential, applied to the input terminal ofthe comparator 81, exponentially decreases in accordance with the timeconstant comprised of capacitance of the capacitor C and the resistanceof the resistor R, while discharging. When a difference of electricpotential between the two terminals of the capacitor C decreases toV_(ref) or less, the output signal V_(out), which is the output from thetimer 75 and timer 76, switches to the low level L from the high levelH. The time for the potential difference between the two terminals ofcapacitor C to become V_(ref) or less, is a predetermined time used forsynchronizing the TV monitor 20 or VCR 21 to a newly selected electronicendoscope. Therefore, the control signals applied to the leads S1′ andS2′, connected to the output terminals of timers 75 and 76, are alsomaintained at the high level until the predetermined time elapses.During this period, video signals are not fed to the TV monitor 20 andVCR 21, etc., and there is no display on the TV monitor 20.

As described above, according to the second embodiment, effects similarto the first embodiment is obtainable.

Note that, in the present embodiments, each of the image-signalprocessing units 42,46, TV monitor 20 and VCR 21 are detachablyconnected to the electronic endoscope selector 10 via connectors (notshown).

The RGB sequential method and the color chip method are mentioned asexamples of image capturing method of an electronic endoscope utilizedin the present embodiments. However, image capturing method of theelectronic endoscope is not limited to the above methods, and anelectronic endoscope may also utilize an ultrasonic endoscope system oran electronic endoscope system that captures a fluorescent image ofexcited cells in the interior of a hollow organ. Further, in the presentembodiments, only two electronic endoscopes or electronic endoscopeunits are described as being connected to the electronic endoscopeselector, although any number of electronic endoscopes may be connected.

In the present embodiments, the RGB component video signals and itssynchronizing signals are used as an example of video signals, videosignals in other format may be used in the present invention, if thecomponents of the video signals are separated from the synchronizingsignals, such as color difference signals and luminance signals.

Although the embodiments of the present invention have been describedherein with reference to the accompanying drawings, obviously manymodifications and changes may be made by those skilled in this artwithout departing from the scope of the invention.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 11-358669 (filed on Dec. 17, 1999), which isexpressly incorporated herein, by reference, in their entireties.

What is claimed is:
 1. An electronic endoscope selector comprising: avideo signal switching processor that switches video signals, which areoutput to at least one peripheral device, from first video signals fedfrom a first electronic endoscope to second video signals fed from asecond electronic endoscope; a synchronizing signal switching processorthat switches synchronizing signals, which are output to said peripheraldevice, from synchronizing signals fed from said first electronicendoscope to synchronizing signals fed from said second electronicendoscope; and a switching control processor that drives said videosignal switching processor and said synchronizing signal switchingprocessor, and suspends output of said video signals for a predeterminedperiod while the switched synchronizing signals are output, thepredetermined period being longer than the time required for thesynchronizing signal to synchronize with said peripheral device,wherein: said switching control processor drives said video signalswitching processor for a predetermined period after driving saidsynchronizing signal switching processor, and suspends output of saidvideo signals during said predetermined period; said video signalswitching processor comprises: a first buffer circuit that receives saidfirst video signals and controls ON and OFF states for outputting saidfirst video signals, wherein said ON state permits output of said firstvideo signals and said OFF state forbids output of said first videosignals; and a second buffer circuit that receives said second videosignals and controls ON and OFF states for output of said second videosignals, wherein said ON state permits output of said second videosignals and said OFF state forbids output of said second video signals;said switching control processor comprises: a first timer that sets saidstate of said first buffer circuit to said OFF state, which forbids theoutput of said first video signals, immediately after input of a controlsignal for setting the output of said first and second buffer circuit tosaid OFF state; and a second timer that sets said state of said secondbuffer circuit to said OFF state immediately after input of said controlsignal and sets said state of said second buffer circuit to said ONstate after said predetermined period from completion of said input ofsaid control signal; and a switching of said video signals is controlledby said control signal, which is alternately input to said first andsecond timer.
 2. A selector according to claim 1, comprising anoperating processor that is used for operating the driving of saidswitching control processor.
 3. A selector according to claim 1, whereinsaid switching control processor drives said video signal switchingprocessor and said synchronizing signal switching processorsimultaneously.
 4. A selector according to claim 1, wherein saidsynchronizing signal switching processor comprises: a third buffercircuit that receives synchronizing signals from said first electronicendoscope and controls ON and OFF states for outputting saidsynchronizing signals, wherein said ON state permits output of saidsynchronizing signals and said OFF state forbids output of saidsynchronizing signals; and a fourth buffer circuit that receivessynchronizing signals from said second electronic endoscope and controlsON and OFF states for output of said synchronizing signals, wherein saidON state permits output of said synchronizing signals and said OFF stateforbids output of said synchronizing signals; and wherein a switching ofsaid synchronizing signals is controlled by alternate switching of saidON and OFF states of said third and fourth buffer circuits.
 5. Aselector according to claim 1, wherein said synchronizing signalswitching processor completes synchronization of the synchronizingsignals before said video signal switching processor outputs the videosignals to said peripheral device.
 6. An electronic endoscope selectorcomprising: a video signal switching processor that switches videosignals, which are output to at least one peripheral device, from firstvideo signals fed from a first electronic endoscope to second videosignals fed from a second electronic endoscope; a synchronizing signalswitching processor that switches synchronizing signals, which areoutput to said peripheral device, from synchronizing signals fed fromsaid first electronic endoscope to synchronizing signals fed from saidsecond electronic endoscope, said synchronizing signal switchingprocessor comprising: a third buffer circuit that receives synchronizingsignals from said first electronic endoscope and controls ON and OFFstates for outputting said synchronizing signals, wherein said ON statepermits output of said synchronizing signals and said OFF state forbidsoutput of said synchronizing signals; and a fourth buffer circuit thatreceives synchronizing signals from said second electronic endoscope andcontrols ON and OFF states for output of said synchronizing signals,wherein said ON state permits output of said synchronizing signals andsaid OFF state forbids output of said synchronizing signals; and aswitching control processor that drives said video signal switchingprocessor and said synchronizing signal switching processor, andsuspends output of said video signals for a predetermined period whilethe switched synchronizing signals are output, the predetermined periodbeing longer than the time required for the synchronizing signal tosynchronize with said peripheral device; wherein a switching of saidsynchronizing signals is controlled by alternate switching of said ONand OFF states of said third and fourth buffer circuits.
 7. A selectoraccording to claim 6, comprising an operating processor that is used foroperating the driving of said switching control processor.
 8. A selectoraccording to claim 6, wherein said switching control processor drivessaid video signal switching processor and said synchronizing signalswitching processor simultaneously.
 9. A selector according to claim 6,wherein said switching control processor drives said video signalswitching processor for a predetermined period after driving saidsynchronizing signal switching processor, and suspends output of saidvideo signals during said predetermined period.
 10. A selector accordingto claim 9, wherein said video signal switching processor comprises: afirst buffer circuit that receives said first video signals and controlsON and OFF states for outputting said first video signals, wherein saidON state permits output of said first video signals and said OFF stateforbids output of said first video signals; a second buffer circuit thatreceives said second video signals and controls ON and OFF states foroutput of said second video signals, wherein said ON state permitsoutput of said second video signals and said OFF state forbids output ofsaid second video signals; and said switching control processorcomprising: a first timer that sets said state of said first buffercircuit to said OFF state, which forbids the output of said first videosignals, immediately after input of a control signal for setting theoutput of said first and second buffer circuit to said OFF state; asecond timer that sets said state of said second buffer circuit to saidOFF state immediately after input of said control signal and sets saidstate of said second buffer circuit to said ON state after saidpredetermined period from completion of said input of said controlsignal; and wherein a switching of said video signals is controlled bysaid control signal, which is alternately input to said first and secondtimer.
 11. A selector according to claim 6, wherein said synchronizingsignal switching processor completes synchronization of thesynchronizing signals before said video signal switching processoroutputs the video signals to said peripheral device.